I don't think you should ever have to hit a child or hurt a child to displine them. You need a confident voice and the commitment and energy to be quick, decisive and consistent.
My son is 18 months old and has been testing the rules now and then. We keep the rules simple. No buttons on the DVD player, no throwing food, be still on the changing table, no hitting, etc. He gets one nicely worded warning and if he disobeys then he gets removed to his playpen immediately with a simple and quick scolding for a 2 minutes time-out. For a 3 year old you can have a time-out chair in an isolated corner.
I've noticed that he's better behaved if I spend quality time playing with a few minutes here and there during the day. "Feeding the Meter". Also, if he's deliberately breaking rules left and right he's usually tired, hungry, in pain or board.
I really like Baby Wise and Happiest Toddler on the Block for references.